Refactor error types: replace generic AacsError/DiscError with typed variants

- Split AacsError { detail } into 13 specific error variants (AacsCertShort,
  AacsAgidAlloc, AacsCertRejected, etc.) with unique error codes E7001-E7012
- Split DiscError { detail } into 7 specific variants (DiscRead, MplsParse,
  ClpiParse, UdfNotFound, DiscNoTitles, DiscTitleRange, DiscNoExtents)
- Add WriteError (E5001), KeydbLoad (E8005), MuxLookahead (E9000), MuxWrite (E9001)
- Add OpenDisc API for single-call open+scan+rip workflow
- Remove all English text from error Display impl (code-only output)
- Normalize doc comments to use -- instead of em dash for ASCII consistency

src/platform/mt1959/variant_a.rs

@@ -12,9 +12,7 @@ const VERIFY_BUFFER_ID: u8 = 0x45;
 pub(super) fn load_firmware(mt: &mut Mt1959, scsi: &mut dyn ScsiTransport) -> Result<()> {
     let firmware = &mt.profile.firmware;
     if firmware.is_empty() {
-        return Err(crate::error::Error::UnlockFailed {
-            detail: "no firmware in profile".into(),
-        });
+        return Err(crate::error::Error::UnlockFailed);
     }
 
     // Upload firmware via WRITE_BUFFER